Agricultural or industrial utility vehicles and especially tractors are typically provided with an interface for adapting an implement to the vehicle in order to perform a work operation. Such an implement could be a plow for example. Such an interface is usually realized by a three point hitch arrangement, comprising two tower draft links and one upper link. As example of such a three point hitch arrangement is known e.g. from FIG. 1 of U.S. Pat. No. 6,830,110.
The attachment sites on the vehicle side for the two draft links and the upper link can be provided at the differential housing or at a hitch- to PTO- (power take off)-housing of the vehicle. An attachment site in the sense of the present invention is especially a site of the housing member onto which a component of the three point hitch arrangement can be mounted or attached to. In this respect, an attachment site can also be referred to as a mounting site.
Furthermore, the three point hitch arrangement usually comprises a rockshaft. The rockshaft is a part which usually is located in a horizontal direction and mounted for rotation within a rockshaft housing or a rockshaft journal. One rocker arm is mounted on the left-hand end of the rockshaft and another rocker arm is mounted on the right-hand end of the rockshaft. Each rocker arm comprises a first end, which is mounted fixed for rotation to the rockshaft, and a second free end, which is spaced apart from the first end. A pair of lift links are provided, each one having an upper end which is pivotally coupled to a draft link respectively. Furthermore, right- and left-hand lift cylinders are provided each one having an upper end which is pivotally coupled to a rocker arm and each having a lower end which is pivotally coupled to the vehicle frame or a housing of the vehicle. Thus, the rockshaft can also be located at the hitch- or PTO-housing or in an additional rockshaft housing, the rockshaft housing mounted on top of the differential case of the vehicle.
This means that usually the single components of the three point hitch arrangement are attached to different components of the vehicle, e.g. the lower draft links are mounted to the frame of the vehicle whereas the upper link and the rockshaft are mounted to the differential case housing. This might result in unequal stress load on those vehicle components caused by a transfer of forces from the implement to the vehicle.
Usually, the PTO transmission is located in the main transmission of the vehicle at the rear end of the vehicle transmission. This means that in a service case related to just the PTO transmission, the housing of the main transmission of the vehicle has to be opened and the relevant parts of the PTO transmission have to be made accessible or the complete main transmission has to be disassembled in order to access the PTO transmission components. This is time consuming and costly.
Accordingly, there is a clear need in the art for providing a three point hitch arrangement as well as a PTO transmission avoiding the aforementioned problems.
FIG. 1 is a schematic representation of a side view of the single components of known prior art a three point hitch arrangement 10 being attached to a differential case 12. The three point hitch arrangement 10 comprises one upper link 14 as well as two lower draft links 16, of which only one can be seen because of the side view of FIG. 1. The upper link 14 comprises a first end 18, which is pivotally engaged with an attachment site 20. The attachment site 20 is located at the rear end of the housing of the differential case 12. The upper link 14 comprises a second end 22, which can be engaged with an implement, the implement is not shown in FIGS. 1 to 5. The draft link 16 comprises a first end 24, which is pivotally coupled to the housing of the differential case 12 at the attachment site 26. The lift cylinder 28 comprises a first end 30 and a second end 32. The first end 30 of the lift cylinder 28 is pivotally connected to the housing of the differential case 12 at the attachment site 34. The second end 32 of the lift cylinder 28 is pivotally connected to the rocker arm 36. The rocker arm 36 comprises a first end 38 and a second end 40. The first end 38 of the rocker arm 36 is connected to the rockshaft 42. The rockshaft housing 44 journals the rockshaft 42 for a pivoting/rotational movement around the longitudinal axis of the rockshaft 42. The rockshaft end 40 of the rocker arm 36 is pivotally connected with the lift link 46. The lift link 46 comprises a first end 48 and the second end 50. The first end 48 of lift link 46 is pivotally connected to the second end 40 of the rocker arm 36. The second end 50 of lift link 46 is pivotally connected with the draft link 16.
Because of the side view of the three point hitch arrangement 10 with its components and the differential case 12, only one rocker arm 36, one lift cylinder 28, one lift link 46 and one draft link 16 is shown. Those elements are also provided on the other side of the three point hitch-arrangement 10, however, they can't be seen from the side view shown in FIG. 1. By changing the length of the left cylinder 28, the rocker arm 36 can be rotated/turned around the longitudinal axis of rockshaft 42. Therefore, an implement being attached to the three point hitch arrangement 10 can be raised or lowered. The three point hitch arrangement 10 being attached to a differential case 12 shown in FIG. 1 is known from the current John Deere 6000 and 7000 series tractors.
FIG. 2 is a schematic representation of a side view of another three point hitch arrangement 10 being attached to a differential case 12 known from prior art. The three point hitch arrangement 10 of FIG. 2 comprises essentially the same components as the one of FIG. 1, namely one upper link 14, two lower draft links 16, two lift cylinders 28, two rocker arms 36, a rockshaft 42 and two lift links 46. These components have essentially the same functionality as the ones shown in FIG. 1. However, the attachment sites 26 for the draft links 16 and the attachment sites 34 for lift cylinders 28 are provided at the housing member 52. The housing member 52 journals the rockshaft 42. Therefore, the rockshaft housing 44 is integrated into the housing member 52. The PTO shaft is indicated by reference numeral 53.
The power take off transmission is neither shown in FIG. 1 nor in FIG. 2. However, the power take off transmission of the embodiments of FIGS. 1 and 2 is located in the main transmission, which is also not shown in FIGS. 1 and 2. The three point hitch arrangement 10 being attached to a differential case 12 shown in FIG. 2 is known from the current John Deere 8000 series tractors.